1. Field of the Invention
The present invention relates to a semiconductor device having a semiconductor chip, and more particularly to a semiconductor device having a flip-chip connected semiconductor chip.
2. Description of the Related Art
With progress in complication of the structure and high performance of the semiconductor device (semiconductor package), a phenomenon that reliability of a connected portion lowers because of a warp of the package, a deformation in the solder ball-connected portion at the time of connection due to a weight of the package, or the like cannot be overlooked. The semiconductor devices having the flip-chip connected semiconductor chip include a type that an external connection terminal for connection to another wiring substrate is disposed on a surface opposite to the surface of the resin substrate to which the semiconductor chip is connected. The external connection terminal accompanies solder balls, and the semiconductor device is mounted and connected to another wiring substrate through the solder balls.
This type of semiconductor device has generally a large stress in the solder balls of the external connection terminal at the corner portions of the package or on just the back surface of the connection position of the semiconductor chip. The stress becomes large at the corner portions of the package because a distance from the center is large, and distortion (generally, distortion in vertical and lateral directions) becomes large accordingly. It is assumed that the stress becomes large just on the back of the semiconductor chip because a thermal expansion coefficient is largely different between the resin substrate and the semiconductor chip, only the deformation of the resin substrate of the package side is restricted to be small by the deformation of the semiconductor chip, another wiring substrate is not restricted, and the solder balls are positioned in a state held between these substrates. Thus, the phenomenon that the deformation of the resin substrate of the package side is restricted to be small by the deformation of the semiconductor chip is more conspicuous in the embodiment that a resin is filled in the space between the resin substrate and the semiconductor chip.
In a case, for example, where a large heat sink is integrally disposed with a package, a deformation of the solder ball connected portions at the time of connection tends to occur due to the weight of the package. The deformation of the solder balls due to the weight occurs to decrease the size in the vertical direction, so that the occurrence of the stress in a shear direction exerts large distortion per unit length accordingly and affects on the reliability. The structures of similar semiconductor devices are disclosed in the following Patent Documents 1 and 2 though the devices are not directly related to the contents of the present application.
[Patent Document 1] Japanese Patent Laid-Open Application No. 2001-35960 (FIG. 4)
[Patent Document 2] Japanese Patent Laid-Open Application No. 2001-156246 (FIG. 16)